Final answer:
The statement is true; substances capable of hydrogen bonding or that display dipole-dipole forces must be polar as these interactions occur due to uneven electron distribution and the presence of a charge separation in a molecule.
Step-by-step explanation:
The statement that substances capable of hydrogen bonding or that have dipole-dipole forces must be polar is indeed True. Hydrogen bonds and dipole-dipole interactions occur when there is an uneven distribution of electrons within a compound, leading to a separation of charge, or polarity. Hydrogen bonding occurs specifically in molecules where hydrogen is covalently bonded to highly electronegative atoms such as nitrogen (N), oxygen (O), or fluorine (F). These bonds create significant polarity due to the large difference in electronegativity between hydrogen and the aforementioned atoms.
Dipole-dipole forces are an intermolecular force that occurs between two polar molecules. For instance, in a hydrogen chloride (HCl) molecule, the chlorine atom, being more electronegative, pulls the shared electrons more towards itself, creating a partially negative charge, while the hydrogen atom becomes partially positive. When many such HCl molecules come together, they align themselves so that the positively charged part of one molecule is near the negatively charged part of another, thus creating dipole-dipole attractions.
All molecules and atoms experience London dispersion forces, but in the case of polar molecules and those capable of hydrogen bonding, these London forces are often weaker compared to the dipole-dipole and hydrogen bonding interactions.